How severe is CVE-2026-34582?

CVE-2026-34582 has a CVSS 3.x base score of 9.1, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability none.

Is CVE-2026-34582 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (14th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-34582?

CVE-2026-34582 affects Botan Project Botan. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-34582?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

Does CVE-2026-34582 have an EU (EUVD) identifier?

Yes. CVE-2026-34582 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-19948.

When was CVE-2026-34582 published?

CVE-2026-34582 was published on 2026-04-07 and last updated on 2026-06-30.

CVE-2026-34582

CVE-2026-34582 is a critical-severity vulnerability in Botan Project Botan with a CVSS 3.x base score of 9.1. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-841.

Key facts

Severity: Critical (CVSS 3.x base score 9.1)
CVSS v4: 8.7
EPSS exploit prediction: 0% (14th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-19948
Weakness: CWE-841
Affected product: Botan Project Botan
Published: 2026-04-07
Last modified: 2026-06-30

Description

Botan is a C++ cryptography library. Prior to version 3.11.1, the TLS 1.3 implementation allowed ApplicationData records to be processed prior to the Finished message being received. A server which is attempting to enforce client authentication via certificates can by bypassed by a client which entirely omits Certificate, CertificateVerify, and the Finished message and instead sends application data records. This vulnerability is fixed in 3.11.1.

Frequently asked questions

What is CVE-2026-34582?: Botan is a C++ cryptography library. Prior to version 3.11.1, the TLS 1.3 implementation allowed ApplicationData records to be processed prior to the Finished message being received. A server which is attempting to enforce client authentication via certificates can by bypassed by a client which entirely omits Certificate, CertificateVerify, and the Finished message and instead sends application data records. This vulnerability is fixed in 3.11.1.
How severe is CVE-2026-34582?: CVE-2026-34582 has a CVSS 3.x base score of 9.1, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability none.
Is CVE-2026-34582 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (14th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-34582?: CVE-2026-34582 affects Botan Project Botan. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-34582?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
Does CVE-2026-34582 have an EU (EUVD) identifier?: Yes. CVE-2026-34582 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-19948.
When was CVE-2026-34582 published?: CVE-2026-34582 was published on 2026-04-07 and last updated on 2026-06-30.

References

Affected products (1)

cpe:2.3:a:botan_project:botan:*:*:*:*:*:*:*:*

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